Machine for treating gears and similar workpieces



Aug. 2, 1966 K. KRETZSCHMAR ETAL MACHINE FOR TREATING GEARS AND SIMILAR WORKPIECES Filed June 25, 1964 4 Sheets-Sheet 1.

INVENTOR. KARL KRETZSCH MAR GERD LICHTENAUER WW4; f

ATTORNEY g 2, 1966 K. KRETZSCHMAR ETAL 3,263,568

MACHINE FOR TREATING GEARS AND SIMILAR WORKPIECES Filed June 25, 1964 4 Sheets-Sheet 3 Fig g INVENTOR. KARL KRETZSCHMAR BY RD LJCHTENAUER Au, 1966 K. KRETZSCHMAR ETAL. 3,

MACHINE FOR TREATING GEARS AND SIMILAR WORKPIECES Filed June 25, 1964 4 sneets shaet 3 Fig, 29

' INVENTOR. KARL KR ETZSCH MAR BY GERD LICHTENAUER g 1.966 K. KRgTzsQHMAm ETAL 63D5W MACHINE FQR TREATING GEARS AND 'SIMILAR WORKPIECES Filed June 25, 1964 4 sheets sheet 4 INVENTUR KARL KRETZSCHHAR Ev GER!) LICHTENAUER ATTORNEY the like.

United States Patent H 49, 15 Claims. c1. 90--1.6)

The present invention relates to machine tools in general, and more particularly to a machine for precision treatment of toothed, threaded, splined or similar workpieces. Still more particularly, the invention relates to a machine which constitutes a further development of machines disclosed in the copending application Serial No. 278,603 of Karl Kretzschmar and now abandoned.

The application of Kretzs'chmar relates to an arrangement for measuring the magnitude and/or direction of stresses which develop in gear finishing machines and For example, such arrangement may be used to determine the magnitude and/ or orientation of stresses acting upon the workpiece, tool, movable work supporting elements and/or movable tool supporting elements in a gear shaving, lapping, grinding or burnishing machine. The stresses may include the main cutting force which brings about removal of shavings, the force which is necessary to effect feed movements of the workpiece with reference to the tool or vice versa, the force which tends to move the too-l radially and away from the workpiece or vice versa, or a resultant of two or more such forces. The measurements are observable on suitable indicating devices and the operator thereupon adjusts the machine in a sense to avoid excessive stresses or to provide for stronger engagement between the workpiece and the tool.

An object of the present invention is to provide an arrangement which responds to impulses obtained on measurements of axial, radial, torsional or other stresses in an automatic or semiautomatic machine and which thereupon adjusts the tool and/or the workpiece in such a way that the magnitude of stresses is kept at an optimum value.

Another object of the invention is to provide an arrangement of the just outlined characteristics wherein measurements of stresses automatically result in appropriate adjustments in the position and/or speed of the tool and/or workpiece so that the operator is not required to read the magnitude of stresses and/or to manually adjust devices which control the magnitude of such stresses.

A further object of the invention is to provide an arrangement which is capable of simultaneously measuring and responding to two or more types of stresses to effect a single adjustment or two or more adjustments.

An additional object of the invention is to provide an arrangement for measuring and responding to stresses between a workpiece and a tool in such a way that the magnitude of stresses will be changed gradually but without any appreciable delay to avoid damage to stressed parts and to insure maximum accuracy in the finish of workpieces.

A concomitant object of the invention is to provide a gear finishing machine which embodies an arrangement of the above outlined characteristics.

Still another object of the invention is to provide an arrangement for measuring and responding to the magnitude of stresses between a cutting, rolling, shaving, lapping, burnishing or other tool and a revolving or stationary workpiece, and to construct the arrangement in such a way that the results of measurements to determine one type of stresses may be used to effect one or more adjustments which, directly or indirectly, lead to elimination of excessive stresses and/ or to increasing cutting, rolling or other engagement which is necessary for optimum treatment of workpieces.

A further object of the invention is to provide an arrangement of the above outlined characteristcs wherein the magnitude of stresses may be measured by very simple, rugged and reliable devices which may consist of commercially available or specially constructed parts and which may effect such measurements in response to changes in hydraulic, pneumatic or mechanical pressure and/or in response to changes in the condition of an electric circuit, depending on the circumstances and on the availability of space for mounting a comparatively large or a compact and lightweight arrangement in an existing gear finishing, thread rolling, splining or other machine.

An additional object of the invention is to provide an arrangement for measuring the magnitude of stresses and for automatically adjusting the pressure between a workpiece and a rotary or reciprocable tool in the form of a gear, worm, roller, hob, rack or the like.

With the above objects in view, one feature of the present invention resides in the provision of a machine for finishing toothed, threaded, splined and similar workpiece-s which comprises a pair of supporting means respectively arranged to carry a tool and a workpiece, drive means for moving the first of these supporting means with reference to the second supporting means so that the tool treats the workpiece whereby the two supporting means are subjected to stresses which tend to change the position thereof, measuring means arranged to oppose and to thus determine the magnitude of stresses acting upon one of the supporting means, and control means for regulating the drive means in response to results of measurements etfected by the measuring means so as to reduce the stresses when the magnitude of axial, radial, torsional or other stresses upon the tool and/ or the workpiece exceeds a predetermined value.

For example, the supporting means for the workpiece may include a tailstock and a headstock with the latter driven by a motor or the like to rotate the workpiece and a shaving tool if the invention is embodied in a gear shaving machine. The supporting means for the tool may comprise a spindle which is tiltable and/ or axially movable to act upon one or more deformable hydraulic, pneumatic, electrical or mechanical pressure-responsive measuring devices which may send impulses to a control device serving to regulate the radial distance between the tool and the workpiece, the feed of the tool in the axial or diagonal direction of the workpiece, the rotational speed of the tool or workpiece, or two or more such movements.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved arrangement itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain specific embodiments with reference to the accompanying drawings, in which:

FIG. 1 is a diagrammatic top plan view of a gear shaving machine which embodies one form of the improved arrangement and wherein such arrangement is used for measuring and regulating the magnitude of radial stresses between a toothed workpiece and a gear-shaped shaving tool;

FIG. 2 is an enlarged view of a detail of the structure shown in FIG. 1, with the tool supporting means illustrated in horizontal section;

FIG. 3 is a vertical section as seen in the direction of arrows from the line III-III of FIG. 2;

FIG. 4 is a partly elevational and partly sectional view of that portion of the arrangement which serves to change the radial distance between the workpiece and the tool;

FIG. 5 is a partly elevational and partly sectional view of a fluid-operated control system which is utilized to automatically regulate the radial distance between the workpiece and the tool by actuating the structure shown in FIG. 4;

FIG. 6 is a partly elevational and partly sectional view of a detail in a modified arrangement wherein the radial distance between a tool and a workpiece is regulated by an electrical control system;

FIG. 6a is a diagram showing the electric circuit for the arrangement of FIG. 6; and

FIG. 7 is a partly sectional diagrammatic view of a third arrangement wherein a fluid-operated control system serves to respond to changes in axial stresses upon the supporting spindle for an axial movable tool.

Referring first to FIG. 1, there is shown a portion of a gear shaving machine which embodies one form of the present invention. The machine comprises a frame 10 which carries a first supporting means including a tailstock 12 and a headstock 13. A gear-shaped workpiece 11a is held between the center 12a of the tailstock 12 and a series of eccentric rotary motion transmitting cones 13a of the headstock 13. This workpiece is rotated by a first motor 14 or by a slowly running second motor 15 through the intermediary of a variable-speed transmission 13]) which is accommodated in the headstock 13.

The frame 10 further carries a second supporting means including a horizontally reciprocable tool slide 16 which may be moved back and forth by a motor 17 through the intermediary of a suitable transmission 17a which rotates a spindle meshing with a spindle nut provided on the slide 16. Alternatively, the slide 16 may be reciprocated by a double-acting hydraulic or pneumatic cylinder or in another suitable way. The guideways 16a for the slide 16 are adjustable with reference to the frame 10 in such a way that the direction in which the slide may reciprocate will be inclined with reference to the axis of the workpiece 11a. This will be necessary when the machine is used for finishing of bevel gears. If the machine is used for crown shaving, the frame supports suitable means for rocking the tool or the workpiece at regular intervals in a manner well known in the art of gear shaving machines.

The slide 16 supports a second slide 18 which is reciprocable in directions radially of the workpiece 11a. This second slide 18 may be moved along ways 18a by means of a handwheel 19 or by a suitable motor, not shown. The slide 16 carries means for fixing the slide 18 in a desired position of radial adjustment with reference to the workpiece.

The front portion of the slide 18 carries a tool holder 20 which is rotatable about the axis of a horizontal shaft 21 shown in FIG. 2. Means are provided for fixing the tool holder 20 in any desired angular position with reference to the shaft 21 so that the axis of the tool 22 may cross in space with the axis of the workpiece 11. This tool 22 is shown in the form of a shaving gear and is mounted on a yieldably supported tool spindle 23 which is rotatable in the eccentric bore of a sleeve 24 so that the tool may be moved closer to or away from the workpiece 11 in response to rotation of the sleeve 24 through the intermediary of a lever 25 which extends radially therefrom, see particularly FIG. 4. Such angular adjustments of the sleeve 24 will be effected to insure controlled and highly accurate removal of shavings or another treatment of the workpiece. In certain positions of the sleeve 24, comparatively large angular displacements of the lever 25 will cause minor radial movements of the tool 22 toward or away from the workpiece 11. The lever 25 is articulately connected with a link 26 which is also connected with a spindle nut 27 meshing with one end portion of an elongated spindle 28. The other end portion of this spindle carries a handwheel 29 by means of which the operator may adjust the angular position of the sleeve 24 to thereby select the exact distance between the tool 22 and workpiece 11.

The spindle 28 has a splined median portion 28a which carries a bevel gear 30. The latter is rotatable in the tool holder 20 and meshes with a second bevel gear 31 provided on the output shaft of an electric motor 32. The bevel gear 30 is free to rotate with reference to the splined portion 28a and will drive the spindle 28 only when its jaw or jaws 30a engage with complementary jaw or jaws 33a of a clutch element 33 which is provided with internal splines so that it cannot rotate with reference ot the spindle 28. As a rule, the housing of the motor 32 accommodates a suitable variable-speed transmission 32a which drives the output shaft 32!) and the bevel gear 31 at a preselected speed to thereby rotate the spindle 28 only when the clutch element 33 engages with the bevel gear 30.

The spindle 28 also comprises a piston 34 which is reciprocable in a fixed cylinder35 and defines with the cylinder two chambers 36, 37 having ports 38, 39, respectively. These ports lead to a control valve 71 which will be described in connection with FIG. 5. The cylinder 35, the piston 34 and the Spindle 28 constitute a drive means for automatically moving the tool 22 radially toward and away from the workpiece 11 in response to changes in the magnitude of stresses between the tool and the workpiece.

A gauge 40 comprises a rodshaped follower 40a which tracks the face of a cam 24a on the periphery of the sleeve 24 whereby the pointer 40b indicates the angular position of the sleeve. The scale 400 of the gauge 40 is preferably calibrated in such a way that it furnishes a reading indicative of the momentary distance between the axes of the tool 22 and workpiece 11. This gauge will be observed by an operator when the sleeve 24 is to be turned by the handwheel 29 or by the motor 32, i.e., not in a fully automatic way.

Referring again to FIG. 2, the tool supporting spindle 23 rotates in an antifriction bearing 41 which is accommodated in the sleeve 24 and which is adjacent to the tool 22. This bearing 41 allows the tool spindle 23 to swivel about a point which coincides with the point where the central plane of the bearing 41 intersects the axis of the spindle 23. That end portion (23a) of the spindle 23 which is distant from the tool 22 is mounted in a needle bearing 42, and this needle bearing is mounted in a small casing 43. As shown in FIG. 3, the casing 43 is free to yield and to oscillate in a plane which passes through the axis of the spindle 23, and is guided by two sets of balls 44 or similar friction reducing elements so that two of its sides may engage two spaced pressure-responsive deformable load cells 60, 61. The screws 44a and plates 44b enable an operator to mount the casing 43 without any lateral clearance, i.e., this casing is guided by two rows of rollers or balls 44 in such a way that it may move toward or away from stress-transmitting engagement with the load cells 60, 61 but should not perform any other movements. Other types of suspending means for the casing 43 may be used if desired, for example, those disclosed in the copending application Serial No. 278,603 of Karl Kretzschmar which is assigned to the same assignee. The load cells 60, 61 and the friction reducing elements 44 are mounted in an annulus 45 which is rotatable without play in a second sleeve 46 rotatably fixed to the sleeve 24. The sleeve 46 may be rotated through the intermediary of a radial lug 47 and is provided with a cover 46a. The lug 47 is bifurcated to receive a screw 48 extending into an arcuate slider 49 which is shiftable in an arcuate groove 50 provided in a rail 50a. The screw 48 also serves to fix the slider 49 in a selected position with reference to the rail 50a. The radial slot 52 in the lug 47 enables the sleeve 46 to allow for changes in radial position of the spindle 23 (with reference to the workpiece 11) when the sleeve 24 is caused to change its angular position with reference to the spindle 23. The position of the load cells 60, 61 will remain substantially unchanged if the angular position of the second sleeve 46 changes because the annulus 45 is mounted in anti-friction bearings 46b, see particularly FIG. 3.

Referring to FIG. 5, it will be noted that the load cells 60, 61 are connected to a common conduit 63 leading to the housing 71a of the control valve 71. This housing accommodates an axially movable valve member 64 and the latter comprises an enlarged portion 65 (hereinafter called plunger). The load cells 60, 61 may be filled with oil or another suitable pressure medium by means of a manually operated pump 66 through a check valve 67. It is to be noted that the hydraulic circuit of FIG. 5 also comprises suitable safety valves, evacuating valves, air removing valves, devices which compensate for changes in viscosity of the pressure medium, and other auxiliaries which are not shown in the drawings. Many such auxiliaries are described and shown in the afore mentioned copending application Serial No. 278,603 to which reference may be had if necessary.

The valve member 64 regulates the flow of pressure medium from a pump P to the chambers 36, 37 of the cylinder 35. The pump P draws oil from a tank 68 through a filter 69 and feeds it through an adjustable pressure regulating valve 70 into the housing 71a. Depending on the axial position of the valve member 64, the oil admitted through the conduit 70a may flow into the conduit 38a or 39a, i.e., to the port 38 or 39. When the conduit 38a receives pressure medium from the conduit 70a, the conduit 39a communicates with a return conduit 73 which discharges spent medium into a collecting conduit 74 leading into the tank 68. Alternatively, the conduit 38a will communicate with a return conduit 72 and with the conduit 74 when the conduit 39a receives pressure medium through the conduit 70a. The conduits 72, 73 or the conduit 74 will preferably comprise suitable throttle valves which insure that the piston 34 operates without axial play, i.e., that the pressure medium escapes from the chamber 36 at the same rate at which it flows into the chamber 37, or vice versa. One such throttle valve is shown at 74a.

The basic operation of the gear shaving machine shown in FIGS. 1 to 5 is well known in the art and need not be described here. When the machine is in operation, the motor 14 or rotates the workpiece 11 and the latter rotates the tool 22. At the same time, the motor 17 reciprocates the slide 16 with the tool 22 so that the tool travels back and forth in directions indicated by arrows 80 and 80a, see FIG. 2. When the tool moves in the direction indicated by arrow 80 or 80a and its teeth mesh with the teeth of the workpiece 11, the work- 1 piece exerts upon the tool a radial pressure or stress indicated by the arrow 81. This pressure is opposed by a force 82 acting in the central plane of the bearing 41, and by a force 83 which is the reaction force of the deformable load cell 60. In other words, the stresses acting in directions indicated by the arrows 82 and 83 balance the stresses acting in the direction indicated by the arrow 81. The end portion 23a of the spindle 23 causes the casing 43 to bear against the load cell 60 with a force 83' which equals the reaction force 83 produced by the load cell 60 whereby the force 83' causes some oil to flow from the cell 60 and into the conduit 63. Some of the oil which is expelled from the cell 60 will flow into the load cell 61 which is smaller and merely serves to insure clearance-free oscillations of the end portion 23a. The remainder of the oil which is expelled from the load cell 60 will flow into the housing 71a and might cause axial movement of the valve member 64 against the bias of a helical return spring 75. The bias of this return spring may be adjusted by a screw 76. As

a rule, the bias of the spring 75 will normally suffice to prevent axial displacement of the valve member 64; however, if the stress upon the load cell 60 exceeds a preselected permissible value (this value is selected by axial adjustment of the screw 76), the valve member 64 moves downwardly, as viewed in FIG. 5, and its plungers 84, 85 allow the pressure medium to flow from the conduit 70a into the conduit 390 as well as to flow from the conduit 38a into the conduit 72 so that the spindle 28 moves upwardly and causes a predetermined angular displacement of the sleeve 24 whereby the radial distance between the tool 22 and the workpiece 11 increases with resultant decrease in the magnitude of the stress 81. When the stress 81 drops to the permissible value, the spring 75 moves the valve member 64 upwardly, as viewed in FIG. 5, and the chambers 36, 37 are again sealed from the conduits 70a, 72. By rotating the annulus 45, the operator may select the direction of the radial force which is to be regulated by the arrangement of FIG. 5. It is to be noted that the second load cell 61 may be replaced by a helical spring, by a set of dished springs, by a dashpot or by any other device which is capable of cooperating with the load cell 60 to insure clearance-free movements of the end portion 23a in response to stresses acting upon the tool 22 on engagement of its teeth with the teeth of the workpiece.

FIGS. 6 and 6a illustrate an electrical control system which is analogous to the one shown in FIGS. 1 to 5. The casing 43 is arranged to act upon a pressure responsive electric switch shown in FIG. 6a. The switch comprises a deformable resistor which changes its resistance in response to changing stresses. For example, this switch may comprise a compressible carbon column 91 which is connected in a suitable bridge circuit shown in FIG. 6a. The bridge circuit also comprises a variable resistor 92, a source U of electrical energy, two constant or variable resistors 93, 94 and a combined impulse generator and amplifier 95 which controls the operation of a drive motor 96 (see FIG. 6) corresponding to the motor 32. It goes without saying that the resistor 90 may be replaced by a deformable device whose capacitance or inductance changes in response to changes in stresses transmitted by the casing 43. It is also possible to use a device whose operation is based on the so-called magnetostrictive effect. It is further possible to replace the bridge circuit of FIG. 6a with a so-called quotient or difierential circuit or to utilize a pressure responsive device whose operation is based on the piezoelectric effect.

In the embodiment of FIGS. 6 and 6a, the switch 90 replaces the load cell 60 and a spring 61a replaces the load cell 61. A spring 20a normally tends to rotate the sleeve 24 in a clockwise direction, as viewed in FIG. 6, and to reduce the distance between the tool and the workpiece. The motor 96 replaces the cylinder 35.

FIG. 7 illustrates a further modification of the present invention. This drawing shows a control system which responds to changes in axial stresses transmitted by the tool supporting spindle 23. While we show a hydraulically operated control system, it is to be understood that such system may be replaced by an electrical or mechanical control system without departing from the spirit of our invention. All that counts is to provide means for measuring the magnitude of axial and/or radial and/ or torsional stresses upon the stress-receiving supporting part or parts, and a device which effects a change in such stresses if the measurement indicates that the stresses are excessive or too small.

The spindle 23 is mounted in such a way that it can move only axially but is held against radial oscillatory movements. Of course, the spindle is free to rotate with the tool 22. The left-hand end portion 23a of this spindle is mounted in two thrust bearings 100, 101 disposed at the opposite sides of a pressure transmitting disk 23b which may act on two axially spaced pressure transmitting deformable load cells 102, 103. The cells 102, 103

a are connected with conduits 104, 105 leading to a common conduit 108. The conduits 104, 105 respectively accommodate adjustable valves 106, 107 which control the flow of a pressure medium between the load cells and the conduit 108. The latter discharges at one end of a housing 109a for a slide valve member 109 which operates in a manner analogous to that of the valve member 64 shown in FIG. 5. Thus, the housing 109a is connected with a supply conduit 114a containing a filter 114 and a pump P and dipping into a tank 115. The supply conduit 114a also contains a pressure regulating valve 116 which may be adjusted by changing the bias of a spring 116a. The housing 109a is further connected with two return conduits 131, 132 leading to a collecting conduit 133 which discharges into the tank 115. The valve member 109 is biased by a helical spring 111 whose bias is adjustable by a screw 111a.

Conduits 125, 126 and 127, 128 connect the housing 10911 with the chambers 119, 118 of a drive means including a double-acting hydraulic cylinder 120 which accommodates a piston 121 having a piston rod 122 with a head 122a. The conduits 125-128 are connected to a distributor valve 129. The valve member 109 comprises plungers 110, 133a, 134 which regulate the flow of a pressure medium from the supply conduit 114a into the conduits 125, 127 and from the conduits 125, 127 to the return conduits 132, 131. The conduits 131-133 may be provided with suitable throttle valves to insure clearance-free movements of the piston 121 in response to admission of a pressure medium into the chamber 118 or 119. A manually operable pump 112 may be utilized to fill the load cells 102, 103 through an adjustable oneway valve 113.

The machine of FIG. 7 operates as follows:

The tool 22 is moved axially in the direction indicated by an arrow 124. The valve 106 is open and the valve 107 is closed. The setting of the distributor valve 129 is such that the conduits 125, 127 respectively communicate with the conduits 126, 128. This means that the load cell 102 is effective. When the tool 22 starts to move in the direction indicated by arrow 124, the load cell 102 is not as yet subjected to any stresses so that the spring 111 biases the valve member 109 upwardly, as viewed in FIG. 7, and the pump P delivers a pressure medium from the tank 115, through the supply conduit 114a, through the conduits 127, 128 and into the chamber 118 of the cylinder 120 so that the piston 121 moves the head 122a in a direction to the right (arrow 124'). At the same time, pressure medium contained in the chamber 119 is free to flow through the conduits 126, 125, 132, 133 and back to the tank 115. The cylinder 120 replaces the motor 17 of FIG. 1 and serves to effect axial movements of the tool 22.

If the axial stress necessary to move the head 122a and tool 22 in the direction indicated by arrows 124, 124' is excessive, the disk 23b transmits such stress to the load cell 102 which sends a stream of pressure medium through the conduits 104, 108 into the housing 109a so that the valve member 109 moves axially against the bias of the spring 111 and reduces the rate at which the pressure medium flows into the chamber 118 so that the axial speed of the tool 22 is reduced. The rate at which the medium flows from the chamber 119 is also reduced to avoid unnecessary axial oscillations of the piston 121.

When the tool 22 is to move in the opposite direction (arrow 123), the valve 106 is closed and the valve 107 is opened. At the same time, the distributor valve is adjusted (as indicated at 129a) so that the pressure medium flows from the supply conduit 114a into the chamber 119 while the medium contained in the chamber 118 may fiow through the return conduit 132 and collecting conduit 133 back to the tank 115. Should the resistance to axial movement of the tool 22 exceed a preselected value, the load cell 103 (which is active when the tool 22 moves in the direction indicated by arrow 123) sends a stream of pressure medium through the conduits 105, 108 so that the slide valve 109 moves against the bias of the spring 111 and reduces the flow of pressure medium from the conduit 114a into the conduit 125.

The machine of FIG. 7 may be modified to utilize an electrically operated control system. In such modified construction, the load cells 102, 103 will be replaced by pressure-responsive switches. Furthermore, the structure shown in FIG. 7 may be incorporated in the machine of FIGS. 1 to 5 or in the machine of FIGS. 6 and 6a so that a single gear finishing machine will comprise a pair of control systems one of which will regulate the magnitude of axial stresses and the other of which will regulate the magnitude of radial stresses between the tool and the workpiece. It is further to be noted that the machine may be modified to regulate the rotational speed of the tool 11 or workpiece 22 by responding to torque instead of responding to axial or radial stresses. When the machine responds to torque, its control system may change the rotational speed, the axial speed of the tool and/or the radial distance between the tool and the workpiece.

In the illustrated embodiments, the tool 22 is used for shaving or other treatment of comparatively large workpieces; however, the novel machine is equally useful for treatment of medium-sized or small workpieces regardless of the position of the workpiece with reference to the tool, i.e., the workpiece may be mounted above, laterally of or at a level below the tool. Also, the machine may be used for treatment of internal gears, for crown shaving of gears and for other types of finishing treatment such as lapping, honing, burnishing, milling, grinding, thread rolling and others.

As mentioned above, radial stresses between the tool and the workpiece may be measured to change the rotational speed and/or the axial speed of the tool and/or workpiece. In other words, and in order to regulate one form of movement of the tool with reference to the workpiece or vice versa, the machine may effect movement of the tool or workpiece in a direction other than the direction of stresses which are measured. For example, and referring to FIG. 7, measurements of axial stresses upon the tool supporting spindle 23 may be used to change the radial distance between the tool 22 and workpiece 11. In FIG. 1, measurements of radial stresses between the tool and the workpiece may be used to change the rotational speed of the workpiece and/ or the axial speed of the tool. This enables the improved machine -to be used with great advantage for so-called rolling (shaving-free generation) of threads, splines and/or teeth on gears, threaded workpieces, splined shafts and similar articles.

In conventional gear shaving and other gear finishing machines, the frame, the work support, the tool support, and the feed mechanism provide a rigid connection between the tool and the workpiece. A serious drawback of such machines is that, in order to avoid the presence of excessive stresses, the arrangement which is used for determining the magnitude of stresses must measure the elastic deformation of parts which can lead to breakage and to belated determination of undesirable stresses. It is also known that the quality of work furnished by a gear shaving machine is affected by the thickness of shavings which are being removed from a toothed workpiece. Thus, the quality of the shaving action will deteriorate if the tool removes shavings of excessive thickness, and removal of excessive shavings often results in unreparable damage to the workpieces. Also, and even if an operator is entrusted with the work of observing a measuring instrument which is used to determine the presence of excessive stresses, the operation of the machine is still dependent on the skill and conscientiousness of the operator because a short interval during which excessive stresses are applied will suffice to cause substantial damage to the workpiece, to the tool, to the supports or to other moving or stationary parts of a complicated machine.

In accordance with the present invention, the likelihood of human error or negligence is eliminated in an exceptionally simple and reliable way, namely, by utilizing the measuring device or devices to produce impulses which are then employed to automatically adjust the stresses as soon as an excessive stress develops. Thus, the machine avoids even short-lasting overstressing of its parts. In other words, by simply employing the measuring device or devices to produce suitable signals or impulses, we insure that a machine can run without supervision and without any danger of excessive or undesirably low stresses so that such a machine can complete the treatment of a gear or the like without necessitating any supervision on the part of the operator, especially if the machine is provided with means for feeding fresh workpieces and for removing treated workpieces. Of course, it is equally possible to construct the improved machine in such a Way that the novel arrangement measures and regulates the stresses during a certain stage in the treatment of a workpiece, especially if the nature of the operation is such that excessive stresses are unlikely to develop during the entire treatment but only when the treatment reaches a certain stage. It was found that the operation of a gear finishing machine is improved beyond expectations if such a machine is provided with the arrangement of our invention, particularly if the arrangement is constructed and assembled in such a way that it is capable of measuring and responding to two or more types of stresses (for example, to radial and axial stresses, to radial and torsional stresses, to axial and torsional stresses, or to a combination of all three types of stresses). If desired, the minimum distance between the axis of a shaving tool and the axis of a toothed workpiece may be determined by rigid blocking elements or stops to insure that the tool cannot remove shavings beyond a certain upper limit which is selected by the positioning of the blocking elements. Such blocking elements are disclosed, for example, in a copending application Serial No. 351,892 of Fritz Hurth.

The results of measurements effected by the arrangement of our invention may be used to change the radial distance between a tool and a workpiece, the axial speed of one or both such parts, diagonal or rocking movements of such parts, rotary movements of one or both parts, or any combination of two or more such movements.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features which fairly constitute essential characteristics of the generic and specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. In a machine for treating toothed, threaded and similar workpieces, in combination, a pair of supporting means respectively arranged to carry a tool and a workpiece; drive means for moving the first of said supporting means with reference to the second supporting means so that the tool treats the workpiece whereby the supporting means are subjected to stresses which tend to change the position thereof; measuring means arranged to oppose and to determine the magnitude of stresses acting upon at least one of said supporting means; control means including means for comparing actual stresses determined by said measuring means with a preselected stress and means for regulating said drive means in response to detection of divergence between said preselected stress and actual stresses determined by said measuring means; and means for determining the minimum distance between the workpiece and the tool.

2. In a machine for treating toothed, threaded and similar workpieces, in combination, a pair of supporting means respectively arranged to carry a tool and a workpiece; drive means for moving the first of said supporting means with reference to the second supporting means in directions to change the radial distance between the tool and the workpiece so that the tool treats the workpiece whereby the supporting means are subjected to stresses which tend to change the position thereof in response to increasing radial pressure between the tool and the workpiece; measuring means arranged to oppose and to determine the magnitude of stresses acting upon at least one of said supporting means; control means including means for comparing actual stresses determined by said measuring means with a preselected stress and means for regulating said drive means in response to detection of divergence between said preselected stress and actual stresses determined by said measuring means so as to increase the radial distance between the tool and the workpiece when the magnitude of actual stresses upon said one supporting means exceeds said preselected stress; and means for determining the minimum distance between the workpiece and the tool.

3. In a machine for treating toothed, threaded and similar workpieces, in combination, a pair of supporting means respectively arranged to carry a pair of cooperating elements one of which constitutes a tool and the other of which constitutes a workpiece; drive means for moving the first of said supporting means with reference to the second supporting means so that the tool treats the workpiece whereby the supporting means are subjected to stresses which tend to change the position thereof in response to axial stresses upon one of said elements; measuring means arranged to oppose and to determine the magnitude of stresses acting upon at least one of said supporting means in response to axial stresses upon said one element; control means including means for comparing actual stresses determined by said measuring means with a preselected stress and means for regulating said drive means in response to detection of divergence between said preselected stress and actual stresses determined by said measuring means so as to reduce the stresses upon said one supporting means when the magnitude of axial stresses acting on said one element exceeds said preselected stress; and means for determining the minimum distance between the workpiece and the tool.

4. In a machine for treating toothed, threaded and similar workpieces, in combination, a pair of supporting means respectively arranged to carry a pair of cooperating elements one of which constitutes a tool and the other of which constitutes a workpiece, one of said elements being arranged to rotate with reference to the other element; drive means for moving the first of said supporting means with reference to the second supporting means so that the tool treats the workpiece whereby the supporting means are subjected to stresses which tend to change the position thereof in response to torque transmitted by said one element; measuring means arranged to oppose and to determine the magnitude of stresses acting upon at least one of said supporting means in response to such torque; control means including means for comparing actual stresses determined by said measuring means with a preselected stress and means for regulating said drive means in response to detection of divergence between said preselected stress and actual stresses determined by said measuring means so as to vary the stresses upon said one supporting means when the magnitude of actual stresses deviates from said preselected stress; and means for determining the minimum distance between the workpiece and the tool.

5. In a machine for treating toothed, threaded and similar workpieces, in combination, a pair of supporting means respectively arranged to carry a cutting tool and a workpiece; drive means for moving the first of said supporting means with reference to the second supporting means so that the tool removes shavings from the workpiece whereby the supporting means are subjected to stresses which tend to change the position thereof in response to removal of shavings from the workpiece; measuring means arranged to oppose and to determine the magnitude 'of stresses acting upon at least one of said supporting means; control means including means for comparing actual stresses determined by said measuring means with a preselected stress and means for regulating said drive means in response to detection of divergence between said preselected stress and actual stresses determined by said measuring means to automatically reduce the thickness of shavings when the magnitude of stresses exceeds said preselected stress; and means for determining the minimum distance between the workpiece and the tool.

6. In a machine for treating toothed, threaded and similar workpieces, in combination, a pair of supporting means respectively arranged to carry a tool and a workpiece; drive means for moving the first of said supporting means radially with reference to the second supporting means so that the tool treats the workpiece whereby the supporting means are subjected to stresses which tend to change the position thereof; measuring means arranged to oppose and to determine the magnitude of stresses acting upon at least one of said supporting means; control means including means for comparing actual stresses determined by said measuring means with a preselected stress and means for regulating said drive means in response to detection of divergence between said preselected stress and actual stresses determined by said measuring means; and means for determining the minimum distance between the workpiece and the tool.

7. In a machine for treating toothed, threaded and similar workpieces, in combination, a pair of supporting means respectively arranged to carry a tool and a workpiece; drive means for moving the first of said supporting means axially with reference to the second supporting means so that the tool treats the workpiece whereby the supporting means are subjected to stresses which tend to change the position thereof; measuring means arranged to oppose and to determine the magnitude of stresses acting upon at least one of said supporting means; control means including means for comparing actual stresses determined by said measuring means with a preselected stress and means for regulating said drive means in response to detection of divergence between said preselected stress and actual stresses determined by said measuring means; and means for determining the minim-um distance between the workpiece and the tool.

8. In a machine for treating toothed, threaded and similar workpieces, in combination, a pair of supporting means respectively arranged to carry a tool and a workpiece; drive means for moving the first of said supporting means with reference to the second supporting means so that the tool treats the workpiece whereby the supporting means are subjected to rnultidirectional stresses which tend to change the position thereof; measuring means arranged to oppose and to determine the magnitude of at least two types of stresses acting upon said supporting means; control means including means for comparing actual stresses determined by said measuring means with a preselected stress and means for regulating said drive means in response to detection of divergence between said preselected stress and actual stresses determined by said measuring means; and blocking means for determining the minimum distance between the workpiece and the tool.

9. In a machine for treating toothed, threaded and similar workpieces, in combination, a pair of supporting means respectively arranged to carry a tool and a work piece; drive means for moving the first of said supporting means with reference to the second supporting means so that the tool treats the workpiece whereby the supporting means are subjected to stresses which tend to change the position thereof; measuring means arranged to oppose and to determine the magnitude of stresses acting upon said supporting means; control means for regulating said drive means in response to results of measurements effected by said measuring means; and blocking means for determining the minimum distance between the workpiece and the tool.

10. In a machine for rolling threads on workpieces, in combination, a pair of supporting means respectively arranged to carry a tool and a workpiece; drive means for moving the first of said supporting means with reference to the second supporting means so that the tool treats the workpiece whereby the supporting means are subjected to stresses which tend to change the position thereof; measuring means arranged to oppose and to determine the magnitude of stresses acting upon at least one of said supporting means; control means including means for comparing actual stresses determined by said measuring means with a preselected stress and means for regulating said drive means in response to detection of divergence between said preselected stress and actual stresses determined by said measuring means; and means for determining the minimum distance between the workpiece and the tool.

11. In a machine for finishing gears and similar workieces, in combination, a pair of supporting means respectively arranged to carry a tool and a workpiece; drive means for moving the first of said supporting means with reference to the second supporting means so that the tool treats the workpiece whereby the supporting means are subjected to stresses which tend to change the position thereof; measuring means including a fluidcontaining pressure-responsive deformable load cell arranged to oppose and to determine the magnitude of stresses acting upon one of said supporting means; fluidoperated control means including means for comparing actual stresses determined by said measuring means with a preselected stress and means for regulating said drive means in response to detection of divergence between said preselected stress and actual stresses determined by said load cell; and means for determining the minimum distance between the workpiece and the tool.

12. In a machine for treating toothed, threaded and similar workpieces, in combination, a pair of supporting means respectively arranged to carry a tool and a workpiece; drive means for moving the first of said supporting means with reference to the second supporting means so that the tool treats the workpiece whereby the supporting means are subjected to stresses which tend to change the position thereof; measuring means including pressure-responsive deformable electric switch means arranged to oppose and to determine the magnitude of stresses acting upon one of said supporting means; electric control means including means for comparing actual stresses determined by said measuring means with a preselected stress and means for regulating said drive means in response to detection of divergence between said preselected stress and actual stresses determined by said switch means; and blocking means for determining the minimum distance between the workpiece and the tool.

13. In a machine for treating toothed, threaded and similar workpieces, in combination, frame means; first supporting means mounted in said frame means and arranged to support a workpiece; second supporting means mounted on said frame means and arranged to support a tool, one of said supporting means being movable with reference to the other supporting means so that the tool may engage and treat the workpiece whereby the two supporting means are subjected to stresses which tend to change the position thereof with reference to each other, one of said supporting means comprising a member arranged to yield to such stresses when the tool engages the workpiece at a rate proportional with the magnitude of such stresses; drive means for moving said movable supporting means; measuring means mounted on said frame and including a pressure-responsive element adjacent to a portion of said yieldable member and arranged to oppose movement of said member in response to said stresses and to thereby determine the magnitude of stresses between the tool and the workpiece, said measuring means further comprising means for producing impulses indicative of the magnitude of stresses opposed by said element; control means operatively connected with said impulse producing means and including means for comparing actual stresses determined by said measuring means with a preselected stress, said control means further including means for regulating said drive means in response to such impulses transmitted thereto by said measuring means which indicate actual stresses different from said preselected stress so that adjustments of said drive means result in a change of actual stresses when the magnitude of such actual stresses deviates from said preselected stress; and blocking means for determining the minimum distance between the tool and the workpiece.

14. In a machine for treating toothed, threaded and similar workpieces, in combination, frame means; first supporting means mounted in said frame means and arranged to support a workpiece; second supporting means mounted on said frame means and arranged to support a tool, one of said supporting means being movable with reference to the other supporting means so that the tool may engage and treat the workpiece whereby the two supporting means are subjected to stresses which tend to change the position thereof with reference to each other, one of said supporting means comprising a member arranged to yield to such stresses when the tool engages the workpiece at a rate proportional with the magnitude of such stresses; drive means for moving said movable supporting means; measuring means mounted on said frame and including a pressure-responsive deformable element adjacent to a portion of said yieldable member and arranged to oppose movement of said member in response to said stresses and to thereby undergo deformation commensurate with the stresses transmitted by said yieldable member; control means operatively connected with said deformable element and including means for comparing actual stresses determined by said measuring means with a preselected stress, said control means further including means for regulating said drive means in response to such deformations of said element which indicate actual stresses different from said preselected stress so that adjustments of said drive means result in a change of actual stresses when the magnitude of such stresses deviates from said preselected stress; and means for determining the minimum distance between the tool and the workpiece.

15. In a machine for treating toothed, threaded and similar workpieces, in combination, frame means; first supporting means mounted in said frame means and arranged to support a workpiece; second supporting means mounted on said frame means and arranged to support a tool, one of said supporting means being movable with reference to the other supporting means so that the tool may engage and treat the workpiece whereby the two supporting means are subjected to stresses which tend to change the position thereof with reference to each other, said second supporting means comprising a tool spindle arranged to yield to such stresses when the tool engages the workpiece at a rate proportional with the magnitude of such stresses; drive means for moving said one supporting means; measuring means mounted on said frame and including a pressure-responsive element adjacent to a portion of said tool spindle and arranged to oppose movement of said tool spindle in response to said stresses and to thereby determine the magnitude of stresses between the tool and the workpiece, said measuring means further comprising means for producing impulses indicative of the magnitude of stresses opposed by said element; and control means operatively connected with said impulse producing means and arranged to regulate said drive means in response to impulses transmitted thereto by said measuring means so that adjustments of said drive means result in a reduction of stresses when the magnitude of such stresses exceeds a predetermined value, said control means comprising a rotary sleeve having an eccentric bore receiving said tool spindle and means for rotating said sleeve in response to impulses received from said measuring means to thereby change the distance between the tool and the workpiece.

References Cited by the Examiner UNITED STATES PATENTS 2,240,795 5/1941 Morgan et a1. 77--32.7 2,601,157 6/1952 LeLan 77-32.7 2,754,567 7/1956 Crane 7732.7 2,774,261 12/1956 Leibing 7732.7 2,950,636 8/1960 Oppenheimer 7732.7 2,978,689 4/1961 Tech et al. 77-32.7

FOREIGN PATENTS 626,058 8/1961 Canada.

WILLIAM W. DYER, 111., Primary Examiner.

G. A. DOST, Assistant Examiner. 

1. IN A MACHINE FOR TREATING TOOTHED, THREADED AND SIMILAR WORKPIECES, IN COMBINATION, A PAIR OF SUPPORTING MEANS RESPECTIVELY ARRANGED TO CARRY A TOOL AND A WORKPIECE; DRIVE MEANS FOR MOVING THE FIRST OF SAID SUPPORTING MEANS WITH REFERENCE TO THE SECOND SUPPORTING MEANS SO THAT THE TOOL TREATS THE WORKPIECE WHEREBY THE SUPPORTING MEANS ARE SUBJECTED TO STRESSES WHICH TEND TO CHANGE THE POSITION THEREOF; MEASURING MEANS ARRANGED TO OPPOSE AND TO DETERMINE THE MAGNITUDE OF STRESSES ACTING UPON AT LEAST ONE OF SAID SUPPORTING MEANS; CONTROL MEANS INCLUDING MEANS FOR COMPARING ACTUAL STRESSES DETERMINED BY SAID MEASURING MEANS WITH A PRESELECTED STRESS AND MEANS FOR REGULATING SAID DRIVE MEANS IN RESPONSE TO DETECTION OF DIVERGENCE BETWEEN SAID PRESELECTED STRESS AND ACTUAL STRESSES DETERMINED BY SAID MEASURING MEANS; AND MEANS FOR DETERMINING THE MINIMUM DISTANCE BETWEEN THE WORKPIECE AND THE TOOL. 